This study investigates the use of inorganic fillers (CaCO3, ZnO, ZrO2, and TiO2)with thermoplastic polyurethane (TPU) as polyethylene terephthalate (PET) coating yarnsto improve their mechanical properties. TPU is the most widely used coating material forthermal melting because of its excellent mechanical properties, functionality, andprocessability. The mechanical properties (e.g., tensile strength and tensile strain) andthermal properties of prepared TPU compounds were investigated with differentinorganic filler contents. TPU resin was melt-mixed using a twin-screw extruder foruniform mixing by filler type and inorganic particle concetration. The core PET yarns weremelt-coated without thermal decomposition at approximately 200 °C. The properties ofthe inorganic filler/TPU compound were analyzed by a universal testing machine, Fouriertransforminfrared spectrometer, differential scanning calorimeter, and dynamicmechanical analysis. The dispersibility of inorganic fillers (ZnO and TiO2) in the TPUs wasbetter than that of CaCO3 and ZrO2. The mechanical properties, thermal properties, andscanning electron microscopy images are ranked in the following order: TiO2 > ZnO >ZrO2 > CaCO3.